1. Field of the Invention
The present invention relates to a method of manufacturing an organic light-emitting device and an organic light-emitting device manufactured using the method, and, more particularly, the present invention relates to a method of manufacturing an organic light-emitting device exhibiting a high light-coupling efficiency, and an organic light-emitting device manufactured using the method.
2. Description of the Related Art
An organic light-emitting device includes an anode, a cathode facing the anode, and an intermediate layer (including an emission layer) positioned between the anode and the cathode. The emission layer of the intermediate layer generates light using holes derived from the anode and electrons derived from the cathode, and the light generated from the emission layer emitted through the anode or the cathode. Thus, an electrode through which light is emitted should have a high transmittance.
In methods of manufacturing organic light-emitting devices, a transparent electrode is formed of Indium Tin Oxide (ITO) or the like. That is, an anode is formed, an intermediate layer is formed on the anode, and a cathode is formed on the intermediate layer using ITO or the like. In organic light-emitting devices, manufactured using these methods, the cathode is formed using sputtering. An image of the cathode thus formed is shown in FIG. 1. However, when forming a cathode using sputtering, an intermediate layer disposed below the cathode can be damaged during the sputtering process. In order to solve this problem, a method of forming a cathode using thermal deposition has been proposed. However, when forming a cathode using a conventional thermal deposition process, the temperature of a substrate for manufacturing the organic light-emitting device reaches about 300° C. At such a high temperature environment, the intermediate layer may be damaged.
In order to solve this problem, a method of forming an anode using ITO or the like and forming a cathode as a reflective electrode on the anode has been proposed. Here, the anode is formed using sputtering, an intermediate layer is formed on the anode, and the reflective cathode is formed using deposition. However, in order to form the intermediate layer interposed between the anode and the cathode, a new material is required instead of a conventional intermediate layer forming material. The intermediate layer positioned between the anode and the cathode can include various suitable layers, such as an electron injection layer, an electron transport layer, a hole injection layer, a hole transport layer, and an emission layer. These layers are formed of materials having appropriate lowest unoccupied molecule orbital (LUMO) levels considering the work functions of the anode and the cathode. However, currently available intermediate layer forming materials are adapted for an anode formed as a reflective metal electrode and a cathode formed as a transparent electrode. Thus, in order to form an anode using ITO or the like, a new intermediate layer forming material needs to be developed, instead of a conventional intermediate layer forming material which is adapted for the work function of a reflective anode and the work function of a cathode formed of ITO or the like.
In view of this problem, a method of forming a cathode as a thin metal double layer, instead of as a transparent electrode, as illustrated in FIG. 2, has been proposed. Referring to FIG. 2, a cathode 20 is a double layer including an Mg layer 21 and an Ag layer 23. In this case, the cathode 20 can have a transmittance value as low as less than 50%, thus providing a relatively high reflectance. As a result, a micro-cavity structure is formed such that reflection repeatedly occurs between an anode 10 formed as a reflective electrode and the cathode 20. Thus, in order to prevent (or reduce) the destructive interference of light, a distance t of an intermediate layer 30 between the anode 10 and the cathode 20 must be controlled.